It is often necessary to quickly obtain a sample of blood and perform an analysis of the blood sample. One example of a need for obtaining a sample of blood is in connection with a blood glucose monitoring system, which a user must frequently use to monitor the user's blood glucose level.
Those who have irregular blood glucose concentration levels are medically required to regularly self-monitor their blood glucose concentration level. An irregular blood glucose level can be brought on by a variety of reasons including illness such as diabetes. The purpose of monitoring the blood glucose concentration level is to determine the blood glucose concentration level and then to take corrective action, based upon whether the level is too high or too low, to bring the level back within a normal range. The failure to take corrective action can have serious implications. When blood glucose levels drop too low—a condition known as hypoglycemia—a person can become nervous, shaky, and confused. That person's judgment may become impaired and that person may eventually pass out. A person can also become very ill if their blood glucose level becomes too high—a condition known as hyperglycemia. Both conditions, hypoglycemia and hyperglycemia, are potentially life-threatening emergencies.
One method of monitoring a person's blood glucose level is with a portable, hand-held blood glucose testing device. The portable nature of these devices enables the users to conveniently test their blood glucose levels wherever the user may be. The glucose testing device includes a test sensor to harvest the blood for analysis. One type of test sensor is the electrochemical biosensors. The electrochemical biosensor includes a regent designed to react with glucose in the blood to create an oxidation current at electrodes disposed within the electrochemical biosensor which is directly promotional to the users blood glucose concentration. Such a test sensor is described in U.S. Pat. Nos. 5,120,420; 5,660,791; 5,759,364; and 5,798,031, each of which is incorporated herein in its entirety. Another type of sensor is an optical biosensor, which incorporates a reagent designed to produce a colorimetric reaction indicative of a users blood glucose concentration level. The colorimetric reaction is then read by a spectrometer incorporated into the testing device. Such an optical biosensor is described in U.S. Pat. No. 5,194,393, which is incorporated herein by reference in its entirety.
In order to check the blood glucose level, a drop of blood is obtained from the fingertip using a lancing device, and the blood is harvested using the test sensor. The test sensor, which is inserted into a testing unit, is brought into contact with the blood drop. The test sensor draws the blood, via capillary action, to the inside of the test unit which then determines the concentration of glucose in the blood. Once the results of the test are displayed on a display of the test unit, the test sensor is discarded. Each new test requires a new test sensor.
Referring now to FIGS. 1 and 2, an example of a testing device 10 and a package 30 of test sensors 12 (“sensor pack”) are shown, respectively. The sensor pack 30 is designed to be housed within the testing device 10. Prior to each test, a collection end 14 of an individual test sensor 12 is pushed by a mechanism within the testing device 10 through its packaging and is extended from the test device 10 through a slot 16 for harvesting a sample of blood. The testing device includes a slider 18 for advancing the test tensor 12. In FIG. 1, a test sensor 12 is shown extending from the testing device 10. The collection end 14 extends from the testing device 10, while a contact end, that is the opposite end of the test sensor 12, remains inside the testing device 10. The contact end includes terminals that electrically couple the electrodes to a meter disposed within the testing device 10 for measuring the oxidation current produced at the electrodes by the reaction of glucose and the reagent. The test unit includes a display 20.
Referring now to FIG. 2, test sensors 12 are shown disposed in the sensor pack 30. The sensor pack 30 is made up of a circular disk 32 having ten individual compartments (blisters) 34 arranged radially. The disk is made from an aluminum foil/plastic laminate which is sealed to isolate the sensor from ambient humidity and from other sensors with a burst foil cover 36. Each test sensor 12 kept dry by a desiccant located inside a desiccant compartment 37 disposed adjacent the blisters 34. To retrieve a sensor, a mechanism disposed within the testing device 10, such as a knife, is driven down through the burst foil into an individual elongated compartment 34 at the end closest to the hub of the disk 32 and then moved radially toward the perimeter of the blister 34 In doing so, the knife engages the contact end 38 (fish tail) of the sensor in that compartment Radial travel of the knife pushes the tip of the sensor out through the burst foil and through parts of the testing device 10 such that the collection end of the sensor 12 is completely out of the testing device 10 and ready to receive a fluid test sample such as blood. For this stage, it is essential that the bond between the base and lid of the sensor withstand the sheer forces generated when the sensor bursts out through the foil. This method of providing a sensor ready for use is more fully described in U.S. Pat. No. 5,575,403, which is incorporated herein by reference in its entirety.
Further details of the operational and mechanical aspects of the testing device 10 and sensor pack 30 are more fully described in U.S. Pat. Nos. 5,575,403; 5,630,986; 5,738,244; 5,810,199; 5,854,074; and 5,856,195, each of which are hereby incorporated by reference in their entireties.
A drawback associated with testing devices which house a package of sensors is that the size of the package (i.e., the number of sensors in the package) is constrained by the device itself, thus making it difficult to modify the number of sensors per package. Accordingly, there exists a need for a testing system wherein the test sensor package size is independent of the testing device.
A drawback associated with the test sensor 12 of the device illustrated in FIGS. 1 and 2 is the somewhat pointed collection end (FIG. 2) of the 14 of the test sensor 12. The pointed end can be inconvenient and uncomfortable in collecting blood. The collection end 12 is pointed to puncture the foil cover 36 as the test sensor 12 is pushed from its individual compartment 34. A test sensor which has a substantially flat, non-pointed, collection end would more conveniently and comfortably collect a sample of blood.